Method and device for pollution reduction from exhausts emissions

ABSTRACT

The disclosed invention relates to a method, an apparatus designed accordingly, to reduce and/or eliminate polluting exhausts components from combustion thermal-generator emissions comprising at least a combustion chamber and at least an fixed exhaust duct. An electric heating resistance able to be activated, following lighting of said combustion heat generator, so as to preheat a catalyst and burn particles deposited on a grille or particles of uncombusted products present initially in the exhaust gases.

FIELD OF THE INVENTION

The disclosed invention relates to a method, an apparatus designed accordingly, to reduce and/or eliminate polluting exhaust components from combustion thermal-generator emissions.

The method and apparatus are intended to be used to reduce and/or eliminate polluting exhaust components from combustion thermal-generator emissions comprising at least a combustion chamber and at least an fixed exhaust duct, the duct be used to direct exhaust from inside volume to outside volume of said combustion chamber.

BACKGROUND OF THE INVENTION

One of the major problems nowadays in highly populated towns and cities is air pollution.

Air pollution is both to substances mixed with air and to substances that modify air natural components. All these substances are commonly named pollutants. Thus we have to pollutants families: direct pollutants and indirect pollutants.

Direct pollutants are typically divided in gaseous pollutant and solid pollutants. As example some direct pollutants are those substances able to modify air oxygen turning it from its bi-atomic molecular state to a modified tri-atomic state (named ozone). This behaviour was originated by exhaust emissions.

In order to reduce pollution and its related damages, the inventors identified pollution sources and thus proper technological intervention for each of the sources was addressed. All of the pollution sources are those that emits gaseous and solid particles in air, they are vehicles, buildings and industrial plants.

The solutions used to reduce the pollutants released in air, their effects on health are different according to type of pollution source, type of pollutant and historical period.

At the beginning the attention was towards the reduction of some pollutants from industrial plants, see as example patent U.S. Pat. No. 5,879,645 that discloses a catalyst and related method to reduce nitrogen oxides from industrial emissions. With emissions they refer principally to combustion exhausts.

Consequently similar solution was applied to a different field such as vehicles, specifically cars, trucks etc.

Effectively, in patent U.S. Pat. No. 5,879,645 a catalyst and related method are applied according to the same scheme to vehicles exhaust. The introduction of catalyzed mufflers allowed reducing drastically pollutants from vehicles.

Nevertheless, is was observed that all these solutions able to reduce pollutants and emissions from industrial plants and internal combustion vehicles are not enough to reduce pollution especially in big cities.

As we anticipated at the beginning it is necessary to reduce pollutants from buildings, too. Residential density contributes substantially to polluting emissions in air mainly due to heating systems and to hot water production systems installed in residential buildings and offices.

Emission reduction is thus mainly related to the reduction of pollutants directly at the source through the introduction of dedicated devices. In order to have a clear advantage it is necessary to install such pollution reducing system on the most of vehicles and residential buildings.

Nowadays most developed countries have regulations that forces automobile producers to sell cars with emission reduction devices to meet specific reduction targets. The mean automobile age made it possible to had the most of circulation cars, which did not adopt such devices, substituted by new existing low emission ones. Unfortunately the residential building situation is different; mean residential building age is so long compared to automobile one that it is not possible to imagine, even in case of regulation similar to automotive field, a fast substitution of the existing device with new ones with low emission profiles. In such case the solutions devoted to residential buildings should be: easy to install on existing plants, have a low cost profile in order not to have a great economical impact on building owners, last for a period comparable to the mean maintenance period and timing of buildings. The mean forecasted lasting time for obsolete components is an important parameter; this time is considerably great in civil field compared to automotive field, indeed are more interesting low impact and revamping solution compared to complete new ones that requires reconstructions.

Each Country issues safety and health regulations related to plant safety especially in case of fire or explosion. In an industrial plant, a catalytic device demands for an high temperature thermal regime. The high temperature is reached by burning gas, gasoline, diesel fuel or others. In a civil building the required modifications for such a device are often incompatible with typology of existing rooms or requires modifications of the environment to satisfy fire and safety regulations especially of explosion-proof regulation in case of gas.

Devices to improve air quality are known for closed environments, such devices suck air from outside changing chemically and mechanically their properties, and pumping inside buildings or in vehicles.

Devices for reducing the pollutants in exhaust gases, of the type described in the following patents are likewise known.

Document DE 19824204 discloses a method and a device for reducing pollutants in exhaust gases produced by combustion in a heater for a house or a dwelling. More particularly the device comprises a combustion chamber, a fixed exhaust duct, means for regulating the pressure of exhaust gases passing through the duct, an air pressure jet system linked to a compressor and a ventilator, and means for separating gaseous pollutants (a noble metal three-way catalyst). The catalyst is, if needed, set to a temperature sufficient for decomposition by a heating element that heats the exhaust gas. The catalyst causes, due to its flow resistance, a pressure loss which is compensated for by the ventilator.

Document DE 19627028 discloses a method and a device for reducing pollutants in exhaust gases produced by combustion in a heater for a house or dwelling. The device comprises a combustion chamber (not shown), a fixed exhaust duct, a ventilator for regulating the pressure of exhaust gases passing through the duct, a ceramic filter for separating particulate pollutants, and an oxidation catalyst for removing gaseous pollutants, which, due to its flow resistance, is able to generate a pressure increase in the duct when the exhaust gas is passing through the catalyst. The catalyst is heated by the exhaust gases to a temperature which is sufficient to decompose the gaseous pollutants. All three units can be positioned at any point in the duct.

Both the apparatus for reducing pollutants described in the two abovementioned German patents have the drawback, which is common to many solutions of the known type, that they are directly arranged on the duct for discharging the exhaust gases. This results in the drawback that it is required to decommission the heat generator in the case where maintenance of the apparatus is required.

These known apparatus, moreover, do not treat adequately the particles in particular of uncombusted products which are released by the heat generator during the repeated lighting operations.

Consequently the catalysts of the apparatus of the known type are not sufficiently protected against the particles which may be deposited and burn on them in particular during the start-up transients of the combustion heat generator.

DISCLOSURE OF THE INVENTION

Therefore the problem underlying the present invention is that of providing a method and an apparatus for reducing and/or eliminating the pollutants present in the exhaust gases produced by combustion heat generators, which may be easily installed in pre-existing plants, which does not have a high cost so as not to discourage installation thereof and which can be easily configured and/or personalized. Another object of the present invention is that of providing a method and an apparatus, the maintenance of which does not involve decommissioning of the heat generator to which it is connected.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical features of the invention, in accordance with the abovementioned objects, may be clearly determined from the content of the claims below and the advantages thereof will emerge more clearly from the following detailed description, provided with reference to the accompanying drawings, which show a purely exemplary and non-limiting embodiment in which:

FIG. 1 shows a system for heating a dwelling using an apparatus according to the invention;

FIG. 2 shows a first example of an apparatus according to the invention in particular for gas oil or gas, associated with a heat generator having an exhaust duct;

FIG. 3 shows a cross-sectional view of the apparatus according to FIG. 2;

FIG. 4 shows a different example of an apparatus according to the invention resting on the ground;

FIG. 5 shows a cross-sectional view of the apparatus according to FIG. 4;

FIG. 6 shows a detail of the apparatus, relating to a protection grille of the catalyst.

DETAILED DESCRIPTION OF A PREFERRED EXAMPLE OF EMBODIMENT

FIG. 1 shows an example of a system for heating a dwelling according to the invention, comprising a combustion heat generator 1 of the known type, which is typically positioned inside the dwelling itself and connected to an apparatus 6 for supplying a fuel 7 and to an exhaust duct 2 (or flue) able to convey the exhaust gases of the heat generator 1 outside the dwelling by means of the apparatus 12 according to the present invention.

The heat generator 1 comprises a combustion chamber 5 able to burn the fuel 7 so as to produce heat. The fuel 7 is fed into the combustion chamber 5 by the apparatus 6 of a type known per se.

Typically the exhaust duct 2 terminates in a chimney 3 which may optionally be equipped with a device 4 for facilitating the introduction and dispersion of the exhaust gases into the atmosphere.

The apparatus 12 has a support structure 20 provided with legs 21 for resting on the ground, as in the case of the example in FIG. 4 which is designed in particular for feeding the heat generator with fuel oil, wood or chippings, or simply with a cylindrical sleeve 22, as in the example of FIG. 2 for gas oil or gas.

As is known, the term “chippings” refers to fragmented wood or wood chips which are obtained by means of special machines. In order to produce chips, inferior quality wood is used, such as that left over from pruning performed in woodland, agricultural or urban areas, Toppings or also the by-products of sawmills. The wood converted into chips may in fact advantageously be used for fuelling purposes, since, being easy to handle, it can be automatically fed into boilers. It should be remembered, however, that in this latter case the size of the chips must be homogeneous and small (3-5 cm).

The abovementioned structure 20 of the apparatus 1 supports a vertically extending pipe 23 having the function of a by-pass for a section of the exhaust duct 2. This by-pass pipe 23 is connected at the top to the exhaust duct 2 and at the bottom to a connecting part 30 (shown in FIGS. 2 and 3) which is in turn connected on opposite sides to the exhaust gas discharge outlet 81 of the heat generator 1 and to the exhaust duct 2. Therefore, the pipe 23 is connected to the exhaust duct 2 by means of two sections, i.e. a first safety section 24 for conveying the exhaust gases from the combustion chamber 5 and a second exhaust gas expulsion section 25 for evacuating them into the atmosphere.

A filter 26, in particular of the mechanical type, is arranged on the by-pass pipe 23, immediately downstream of the connecting part 30. This filter 26, in the case of fuels likely to produce a considerable amount of residual combustion product, as for example in the case fuel oil or chippings, is advantageously of the cyclone (or vortex) type since it allows a significant reduction in the solid particles suspended in the exhaust gases by means of a separating action due to the centrifugal force.

By way of an indication, this filter allows a reduction in the particles present in the fuel oil and in the chippings from an amount, respectively, of about 50 mg Nm³ and 100 mg Nm³ down to an amount of about 5 mg Nm³ (miligrammes per normal cubic metre).

As can be seen in FIG. 5, the exhaust gases leaving the combustion chamber 5 via the connecting part 30 (not shown) rise up through the central tube 27 and then descend inside the individual conically shaped cyclones 28, being forced to perform a rotating movement. This movement, owing to the action of the centrifuging force, produces a separation of the solid particles which consequently fall into the underlying container means 29 (consisting, for example, of an extractable drawer for emptying the accumulated material), leaving the exhaust gas purified and free to rise up again along the central channel until it emerges from the upper outlets 31.

In order to optimize the efficiency of the filter, depending on the power of the heat generator 1, only a corresponding number of the outlets 31 are advantageously open. With reference to the example shown in the accompanying figures it may be considered that each cyclone 28 processes on average 90 cubic metres per hour of exhaust gases and that the 12 cyclones envisaged will all be open in order to meet the requirements of a 350 kW heat generator.

Moreover, preferably in order to reduce the production costs, the cyclones 28, except for the outlets 31, are incorporated in a single cylindrical body which is formed as one piece by means of casting.

In the case where the heat generator 1 is intended to be fed with gas oil or with gas, or with products producing a small residual amount of suspended particles after combustion, it is possible to provide a simpler and less costly mechanical filter 26, for example consisting of a simple meshwork.

The by-pass pipe 23 also has, arranged inside it in succession, an electric heating resistance 40, an exhaust gas intercepting grille 41, a catalyst 42 and suction means 43 preferably consisting of a centrifugal ventilator.

From an operational point of view, when the ventilator 43 is switched off or not operating, the exhaust gases do not pass through the by-pass pipe 23 where the filter 26, the catalyst 42 and the grille 41 are located, since these act like a bung causing a slight loss of pressure, but instead pass through the connecting part so as to reach directly the exhaust duct 2 via the first section 24.

On the other hand, when the ventilator is operated, the exhaust gases are instead forced to circulate inside the pipe 23 so as to subject the flow to treatment by the filter 26, the catalyst 42 and the grille 41.

The electric resistance 40 is preferably activated only during the very initial stages of operation of the apparatus 12 or whenever the combustion heat generator is started up or restarted. It performs the dual function of burning the particles deposited on the grille 41 during the previous operating cycle of the heat generator and pre-heating the catalyst 42 prior to arrival of the exhaust gases.

More specifically, upon ignition of the flame of the heat generator, which can be directly detected by the start signal or by means of a pressure sensor 50, for example, arranged downstream of the combustion chamber and sensitive to the arrival of the shockwave caused by ignition of the flame, the electric resistance 40 heats up and in a few seconds by means of irradiation heats the surface of the grille 41 to a temperature of between 400 and 700° C. so that it burns all the carbon-containing particles which are deposited on it during the previous operating cycle of the heat generator.

At the same time, the resistance 40 heats up the catalyst 42 so as to allow it to be already fully operative already before arrival of the exhaust gases. The same catalyst 42 is able to treat the emissions produced by the particles which burn on the grille 41.

For example, it is possible to envisage that with a 300 kW heat generator it is sufficient to provide a resistance with a power of 6 kW intended to remain switched on during the initial stage of operation of the apparatus or whenever the heat generator is restarted, for a period of 10 to 120 seconds. The consumption of the resistance 40, which is advantageously intended only to produce heat by means of irradiation, is therefore practically negligible.

Moreover, owing precisely to the presence of the resistance 40, it is possible to consider that the grille 41 is practically advantageously of the self-cleaning type.

Once the catalyst 42 has been heated up and before the exhaust gases reach the apparatus 12 (the exhaust gases travel relatively slowly so as to release heat inside the exchanger of the heat generator 1), the ventilator 43 is switched on, regulating its flowrate so that it conveys the entire exhaust gas flow leaving the heat generator through the by-pass pipe. Basically, the power required of the ventilator is minimal and equal to the loss of pressure inside the by-pass pipe due to the presence of the filter 26, the grille 41 and the catalyst 42. In this way, the apparatus does not modify the operating conditions of the heat generator 1, which is not affected at all by operation of the apparatus 12.

Advantageously, the speed of the motor of the ventilator 43 is regulated by means of an inverter which is controlled depending on the flowrate of the exhaust gases leaving the heat generator 1, which is, for example, detected by a special flow meter.

In accordance with the embodiment shown in FIG. 6, the grille 41 is composed of several superimposed sheets 41′ of metal meshes 44 which have dimensions increasing in the direction of the resistance 4.

The present invention also relates to a method for reducing or eliminating the pollutants present in the exhaust gases produced by combustion heat generators. For the sake of simplicity of the description, the same terms already adopted with reference to the apparatus 12 will be used.

The method therefore envisages a step involving treatment of the exhaust gases which are circulated by the ventilator 43 inside the vertically extending by-pass pipe 23.

Treatment of the exhaust gases envisages filtering, in particular by means of a centrifugal action, in order to purify them of the polluting solid particles, as well as conveying them through the catalyst in order to eliminate the polluting gases.

In accordance with the idea underlying the present invention, the method envisages that, during start-up of the apparatus 12 following lighting of the heat generator 1, with the suction means 43 initially switched off, heating of the grille mounted inside the by-pass pipe 23 is performed by means of the electric heating resistance 40, so as to burn particles deposited on the grille 41 and preheat the catalyst 42.

The heating step is transitory and terminates when the suction means are switched on, namely soon afterwards, so as to allow the grille to burn also the particles of uncombusted products present in the first fumes produced by lighting of the heat generator.

The invention thus conceived therefore achieves the predefined objects.

Obviously, it may also assume, in its practical embodiment, forms and configurations different from that illustrated above without thereby departing from the present scope of protection.

Moreover, all the details may be replaced by technically equivalent elements and the dimensions, forms and materials used may be any depending on the requirements. 

1. Apparatus for reducing or eliminating the pollutants present in the exhaust gases produced by combustion heat generators provided with a combustion chamber and an exhaust duct for guiding said exhaust gases from the inside to the outside of said combustion chamber, characterized in that it comprises: a support structure; a vertically extending pipe arranged so as to by-pass a section of the exhaust duct, supported by said support structure and connected to the exhaust gas discharge outlet of the heat generator 1 and to the exhaust duct by means of two sections, i.e. a first safety section for conveying the exhaust gases from the combustion chamber and a second section for expelling the exhaust gases treated inside the apparatus; a filter, in particular of the vortex type, mounted on said by-pass pipe so as to intercept said exhaust gases and purify them of polluting solid particles; an electric heating resistance mounted on said by-pass pipe and arranged downstream of said filter; at least one grille mounted on said by-pass pipe so as to intercept said exhaust gases and arranged downstream of said electric heating resistance; at least one catalyst mounted on said by-pass pipe so as to intercept said exhaust gases and arranged downstream of said grille; suction means, able to produce, when switched on or off, selectively the circulation respectively of said exhaust gases in said by-pass pipe or in the section of the exhaust duct situated between said first and second section for connection to said by-pass pipe; said electric heating resistance being able to be at least temporarily activated, in particular following lighting of said combustion heat generator, so as to preheat said catalyst and burn particles deposited on said grille or particles of uncombusted products present initially in the exhaust gases.
 2. Apparatus according to claim 1, characterized in that removable container means, in particular of the drawer type, are envisaged for storing said polluting solid particles.
 3. Apparatus according to claim 1, characterized in that said electric heating resistance faces said grille which heats up as a result of irradiation to a temperature of between 400 and 700° C.
 4. Apparatus according to claim 1, characterized in that said grille is composed of several superimposed sheets.
 5. Apparatus according to claim 4, characterized in that the metal meshes of said superimposed sheets have dimensions decreasing in the direction of said catalyst and dimensions increasing in the direction of said resistance.
 6. Method for reducing or eliminating the polluting components present in the exhaust gases produced by combustion heat generators provided with a combustion chamber and with an exhaust duct for guiding said exhaust gases from the inside to the outside of said combustion chamber, characterized in that it comprises: a step involving treatment of the exhaust gases coveyable by suction means inside a vertically extending pipe arranged so as to by-pass a section of the exhaust duct and connected to the exhaust gas discharge outlet of the heat generator 1 and to the exhaust duct by means of two sections, i.e. a first safety section for conveying the exhaust gases from the combustion chamber and a second section for expelling the exhaust gases treated in the apparatus; said exhaust gas treatment step envisaging: at least one filtering operation, in particular by means of a centrifugal action, able to purify the exhaust gases of polluting solid particles; at least one operation of conveying the exhaust gases through the catalyst so as to eliminate the polluting gases present in them; said method also comprising a step involving start-up of the apparatus following lighting of the generator, wherein said suction means are initially switched off and wherein heating of at least one grille mounted on said by-pass pipe for intercepting said exhaust gases is performed by means of an electric heating resistance, so as to pre-heat said catalyst, in order to burn the particles deposited on said grille during the previous operating cycle of the heat generator.
 7. Method according to claim 6, characterized in that said heating step is transitory and takes place until said suction means are switched on.
 8. Method according to claim 6, characterized in that said heating step is transitory and has a duration in the range of 10 to 120 seconds.
 9. Method according to claim 6, characterized in that said suction means are started up following lighting of the heat generator and in time to convey inside the by-pass pipe the first exhaust gases produced by the heat generator 1 after being lit, so that the particles of uncombusted products present in the exhaust gases burn on said grille heated by said electric resistance. 